title: Sphingosine kinases are not required for inflammatory responses in macrophages.
abstract: Sphingosine kinases (Sphks), which catalyze the formation of sphingosine 1-phosphate (S1P) from sphingosine, have been implicated as essential intracellular messengers in inflammatory responses. Specifically, intracellular Sphk1-derived S1P was reported to be required for NFκB induction during inflammatory cytokine action. To examine the role of intracellular S1P in the inflammatory response of innate immune cells, we derived murine macrophages that lack both Sphk1 and Sphk2 (MΦ Sphk dKO). Compared with WT counterparts, MΦ Sphk dKO cells showed marked suppression of intracellular S1P levels whereas sphingosine and ceramide levels were strongly up-regulated. Cellular proliferation and apoptosis were similar in MΦ Sphk dKO cells compared with WT counterparts. Treatment of WT and MΦ Sphk dKO with inflammatory mediators TNFα or Escherichia coli LPS resulted in similar NFκB activation and cytokine expression. Furthermore, LPS-induced inflammatory responses, mortality, and thioglycolate-induced macrophage recruitment to the peritoneum were indistinguishable between MΦ Sphk dKO and littermate control mice. Interestingly, autophagic markers were constitutively induced in bone marrow-derived macrophages from Sphk dKO mice. Treatment with exogenous sphingosine further enhanced intracellular sphingolipid levels and autophagosomes. Inhibition of autophagy resulted in caspase-dependent cell death. Together, these data suggest that attenuation of Sphk activity, particularly Sphk2, leads to increased intracellular sphingolipids and autophagy in macrophages.
authors.affiliation: From the Center for Vascular Biology, Department of Pathology and Laboratory Medicine.
authors.forename: Yuquan
authors.initials: Y
authors.lastname: Xiong
authors.affiliation: From the Center for Vascular Biology, Department of Pathology and Laboratory Medicine,; Department of Medicine.
authors.forename: Hyeuk Jong
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: INSERM U970, Paris Cardiovascular Research Centre, 75015 Paris, France,; the Université Paris-Descartes, 75015 Paris, France.
authors.forename: Boubacar
authors.initials: B
authors.lastname: Mariko
authors.affiliation: From the Center for Vascular Biology, Department of Pathology and Laboratory Medicine.
authors.forename: Yi-Chien
authors.initials: YC
authors.lastname: Lu
authors.affiliation: Department of Medicine.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Dannenberg
authors.affiliation: Department of Biochemistry, Weill Cornell Medical College, Cornell University, New York, New York 10065.
authors.forename: Abigail S
authors.initials: AS
authors.lastname: Haka
authors.affiliation: Department of Biochemistry, Weill Cornell Medical College, Cornell University, New York, New York 10065.
authors.forename: Frederick R
authors.initials: FR
authors.lastname: Maxfield
authors.affiliation: INSERM U970, Paris Cardiovascular Research Centre, 75015 Paris, France,; the Université Paris-Descartes, 75015 Paris, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Camerer
authors.affiliation: NIDDK, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Proia
authors.affiliation: From the Center for Vascular Biology, Department of Pathology and Laboratory Medicine,. Electronic address: tih2002@med.cornell.edu.
authors.forename: Timothy
authors.initials: T
authors.lastname: Hla
mesh_terms: D000818:Animals; D001343:Autophagy; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D007249:Inflammation / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D008070:Lipopolysaccharides / Q000633:toxicity; D008246:Lysophospholipids / Q000096:biosynthesis* / Q000235:genetics; D017737:Macrophages, Peritoneal / Q000201:enzymology* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000235:genetics; D000099157:Sphingosine Kinase
chemical_list: D020169:Caspases; D008070:Lipopolysaccharides; D008246:Lysophospholipids; D017853:Phosphotransferases (Alcohol Group Acceptor); D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate
keywords: Autophagy; Ceramide; Inflammation; Lysosomes; Macrophages; Sphingolipid; Sphingosine 1-Phosphate